From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6DCBB36E47E; Tue, 16 Jun 2026 17:10:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781629830; cv=none; b=ASgR4reg5nhqIvQu/5J76KM7wn1/BnvibhO/4OJ7VDkvHsNE7u2CrvHrWGi2iP7Jo0hckd+c6Kgk7xzogvpgRYmyg2/IN88QR+Lrcel+kmO0VNh6QZrP6LKevDUn7Hfs8/9oIO3KqEt3cTuT+8a66vO3MOSXISIgmzRTNaPTLyk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781629830; c=relaxed/simple; bh=RTX4U71STQmVwiFVRdxn9dk8DftV30HipESGs4DKWDs=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=SI/1b8MEdpY2mgd27vGO0NQK7NfD3VJ+kNXEMOGswjCoI56mlG/Wxr1xpkHTgmvuifoo0m53JwhiBXs8qqpoLRDRJfUcogFCTFl78wFqmHn7Q0EChktaxndWq4GXwR5fJ1vf7aenY1jvp3QFGClhilrwDL44IPchlP0176xLTps= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=2tQ5ngZC; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="2tQ5ngZC" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B12E51F000E9; Tue, 16 Jun 2026 17:10:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1781629829; bh=rUlaUZvQKKp9ZBmnkrmn4vm/p31GFZhg1TeFhj5iI/U=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=2tQ5ngZCp77dGmYwY09bGD9v9eWQ922iUriXzWfui3CUQ3OSUJlV3TeAmS5pyJu0f YWVwdZjCohHdMZ4EIxhJDfLd9UI2q27hXisrSXBUk3zBlm/hGAETSMi4Xo4LEoUyI1 pXjgblz+Wnc3a+5QmCOIF2SfHx3n8imrm8kwUnx8= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Bjorn Andersson , Srinivas Kandagatla Subject: [PATCH 6.6 360/452] slimbus: qcom-ngd-ctrl: Avoid ABBA on tx_lock/ctrl->lock Date: Tue, 16 Jun 2026 20:29:47 +0530 Message-ID: <20260616145136.027966247@linuxfoundation.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260616145117.796205997@linuxfoundation.org> References: <20260616145117.796205997@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Bjorn Andersson commit 55f2ea9ff83cc27a85526b14bc9b32f96a08d6ec upstream. During the SSR/PDR down notification the tx_lock is taken with the intent to provide synchronization with active DMA transfers. But during this period qcom_slim_ngd_down() is invoked, which ends up in slim_report_absent(), which takes the slim_controller lock. In multiple other codepaths these two locks are taken in the opposite order (i.e. slim_controller then tx_lock). The result is a lockdep splat, and a possible deadlock: rprocctl/449 is trying to acquire lock: ffff00009793e620 (&ctrl->lock){+.+.}-{4:4}, at: slim_report_absent (drivers/slimbus/core.c:322) slimbus but task is already holding lock: ffff00009793fb50 (&ctrl->tx_lock){+.+.}-{4:4}, at: qcom_slim_ngd_ssr_pdr_notify (drivers/slimbus/qcom-ngd-ctrl.c:1475) slim_qcom_ngd_ctrl which lock already depends on the new lock. Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&ctrl->tx_lock); lock(&ctrl->lock); lock(&ctrl->tx_lock); lock(&ctrl->lock); The assumption is that the comment refers to the desire to not call qcom_slim_ngd_exit_dma() while we have an ongoing DMA TX transaction. But any such transaction is initiated and completed within a single qcom_slim_ngd_xfer_msg(). Prior to calling qcom_slim_ngd_exit_dma() the slim_controller is torn down, all child devices are notified that the slimbus is gone and the child devices are removed. Stop taking the tx_lock in qcom_slim_ngd_ssr_pdr_notify() to avoid the deadlock. Fixes: a899d324863a ("slimbus: qcom-ngd-ctrl: add Sub System Restart support") Cc: stable@vger.kernel.org Signed-off-by: Bjorn Andersson Signed-off-by: Srinivas Kandagatla Link: https://patch.msgid.link/20260530204421.116824-9-srini@kernel.org Signed-off-by: Greg Kroah-Hartman --- drivers/slimbus/qcom-ngd-ctrl.c | 3 --- 1 file changed, 3 deletions(-) --- a/drivers/slimbus/qcom-ngd-ctrl.c +++ b/drivers/slimbus/qcom-ngd-ctrl.c @@ -1469,15 +1469,12 @@ static int qcom_slim_ngd_ssr_pdr_notify( switch (action) { case QCOM_SSR_BEFORE_SHUTDOWN: case SERVREG_SERVICE_STATE_DOWN: - /* Make sure the last dma xfer is finished */ - mutex_lock(&ctrl->tx_lock); if (ctrl->state != QCOM_SLIM_NGD_CTRL_DOWN) { pm_runtime_get_noresume(ctrl->ctrl.dev); ctrl->state = QCOM_SLIM_NGD_CTRL_DOWN; qcom_slim_ngd_down(ctrl); qcom_slim_ngd_exit_dma(ctrl); } - mutex_unlock(&ctrl->tx_lock); break; case QCOM_SSR_AFTER_POWERUP: case SERVREG_SERVICE_STATE_UP: